Conventionally, an uninterruptible power supply device is widely used as a power supply device for stably supplying alternating-current (AC) power to an essential load such as a computer system. For example, as disclosed in Japanese Patent Laying-Open No. 07-298516 (Patent Literature 1), the uninterruptible power supply device generally includes a converter converting commercial AC power into direct-current (DC) power, an inverter converting the DC power into AC power and supplying the AC power to a load, a chopper supplying the DC power generated by the converter to a battery at the time of receiving the commercial AC power and supplying the DC power of the battery to the inverter at the time of interruption of the commercial AC power, and a control unit controlling the entire device.